This invention relates to a cartridge razor which includes a handle and a cartridge carrier mounted to the handle in a way which allows the cartridge to rotate relative to the handle about an axis which is perpendicular to the edge of a blade of the cartridge and parallel to the surface to be shaved, thereby to accommodate changing contours of a surface to be shaved.
Twin-blade cartridges which swivel about an axis parallel to the blade edges are well-known. Such swivelling improves contact between the blades and the surface being shaved, and it has been found that the swivelling about the orthogonal axis improves blade contact, end to end. See GB-A-2116470 and GB-A-2172236.
Although the razor of GB-A-2116470 provides improved conformance with facial contours, end to end of the shaving cartridge, there is scope for further improvement and it is one object of the present invention to achieve such an improvement. What is required is a way of mounting the cartridge to the handle which allows the cartridge to move smoothly and with a minimum of friction about the axis perpendicular to the blade edge or edges, whenever there is a change of the angle between the handle and the surface being shaved. Further, the mounting should be compact enough not to interfere unduly with the user""s vision of the area being shaved, or with subsequent rinsing of the cartridge.
A cartridge razor of the type initially defined above, and in accordance with the present invention, is characterized in that the rotation perpendicular to the edge of a blade of the cartridge i.e. end-to-end rocking movement of the cartridge is about an axis of rotation which lies either on or below the said surface to be shaved.
By so locating the rotation centre, it is possible to establish a stable reaction to changing contours of the surface being shaved, which ensures that the end to end rocking movements of the cartridge do not involve any motion in the line of the blade edges relative to that surface.
Conventional swivelling movement parallel to the edge of the or each blade of the cartridge can be provided between a cartridge carrier and the cartridge. Preferably, the axis of rotation of the cartridge parallel to the blade edge(s) is also on or below the surface to be shaved. When the two orthogonal rotational axes intersect, the combination of the two swivel axes creates and effective universal joint on or below the surface being shaved.
The cartridge carrier can itself be carried on a four-bar linkage which lies in a plane parallel to the blade edges. A suitable four-bar linkage has first and second transverse links, each with a mid-point pivotally mounted to the handle, and two opposite ends each pivotally mounted to an extension link, itself mounted pivotally to the end of the cartridge carrier, so that each end of the carrier is supported by one of the extension links of the four-bar linkages.
Conveniently, each of the four-bar transverse links is a bell crank having an apex at its mid-point and cranked left hand and right hand limbs extending in opposite directions from the apex but subtending an angle of less than 180xc2x0, for example, 60xc2x0, so that the bell crank points, like an arrow head, towards the cartridge carrier. This is one effective way to move the centre of rotation of the carrier away from its mounting in the handle and towards the desired position on or behind the surface to be shaved.
A four-bar linkage as described immediately above has already been disclosed, see GB 1460732, but only as a pair of such linkages, to provide swivel motion about the axis parallel to the blade edges. The rotational axis is above the surface to be shaved.
Preferably, a biasing spring is provided, to urge the carrier to a start disposition so that during shaving whenever the cartridge is no longer subject to forces tending to rotate it about the rotational axis perpendicular to the blade edges, the biasing means will urge the carrier back to its start disposition. A preferred biasing spring is a resilient wishbone mounted at its apex to the said bell crank and with its limbs pressing against the two extension links.